Rolling screen mechanisms have become increasingly popular in recent years. Rolling screens provide all of the advantages of traditional hinged screen doors, while affording additional benefits of appearance and convenience. Further, rolling screens can be installed in certain applications, such as french doors, where traditional screens cannot be used.
There are several descriptions of conventional rolling screen mechanisms in the patent literature. For example, U.S. Pat. No. 6,666,252 to Welfonder is directed to a winding mechanism for controlling the retraction and deployment of an architectural covering, such as a window blind or shade having a winding element 12, about which the covering, or its lift cord or tapes are wound and unwound with rotation of the winding element about a first axis of rotation, and a fluid brake 40 for retarding the rotation of the winding element in at least one direction about the first axis. The fluid brake comprises a fluid tight compartment 42 containing a liquid and an impeller 46. The compartment and the impeller are adapted for relative rotation about a second axis, which can be the same as or coaxial with the first axis. Either the compartment or the impeller is operatively connected to the winding element. In operation the liquid rotates with the rotation of the compartment or the impeller about the second axis. Rotation of the liquid relative to the impeller or to the compartment in at least a first direction about the second axis is effective to retard the rotation of the winding element in at least a second direction about the first axis. The impeller 46, or a peripheral wall surface 43 of the compartment 42 has a first surface 49B that extends generally radially and substantially parallel with respect to the second axis.
U.S. Pat. No. 6,629,555 to DeBlock discusses a retractable screen door for drawing a flexible screen panel across an opening, including a flexible screen wound around a spring biased take-up shaft, and guide rails for guiding the screen as it is moved across the opening. A unique latch mechanism is disclosed, said latch mechanism being located in the guide rails. Further, the screen may include an adjustable gear assembly for changing the tension on the spring. The retractable screen is optionally designed to have the appearance of a common door casing.
U.S. Pat. No. 6,591,890 to Grubb sets forth a retractable screen mechanism having two tracks mounted on opposing sides of an opening and a screen with a screen material mounted on a frame having two flexible opposing sides corresponding to and adapted to engage the two tracks. A spool mechanism for winding up the screen extends between the flexible opposing sides and engages a third side of the frame and is biased to a wind up position. The spool mechanism has a speed reducer which comprises a resistance structure moving through a viscous fluid to reduce the speed of the biased screen when moving to the wind up position.
U.S. Pat. No. 4,848,522 to Wolf deals with a safety device for preventing accidental unrolling of a rolling shutter or overhead door comprising a cogwheel which has uniformly distributed on the circumference opening outward for containing radially movable tumblers, a cage which surrounds the cogwheel that contains an abutment in the form of a recess for the tumblers which are raised by the action of centrifugal force. Upon reaching a predetermined rotational speed, the tumblers engage an abutment in the cage and the cage acting as a brake is then driven by the cogwheel and slowed down by friction.
U.S. Pat. No. 4,188,992 to Segerljung discusses a braking device for roller blind spring loaded rods compressing a sleeve affixed to the end of the rod carrying therein several radially movable weight segments. The shaft upon which the rod rotates carries at least one non-rotatable braking element. The centrifugal force generated on the weight segments upon a rapid rotation of the rod forces the segments to press against the braking elements slowing the rod down by friction braking. The braking elements can be flange discs mounted on or affixed to the shaft.
Although some rolling screen systems provide retraction mechanisms, only a few provide the safety of speed reduction. Unfortunately, those that do provide speed reduction use oil or other viscous fluids to provide resistance. Such fluids are subject to wide variations in effective viscosity with varying ambient temperatures. As a result, screen retraction can occur too quickly in hot conditions, or barely at all in cold climates. It can be seen from the foregoing that the need exists for a simple, inexpensive speed reducer for rolling screen systems that are relatively impervious to temperature fluctuations, thus overcoming the deficiencies of known arrangements.